Statements and Statement Blocks - Perl

If functions are the verbs of Perl, then statements are the sentences. Instead of a period, a statement in Perl usually ends with a semicolon, as we saw earlier:

print "Hello, world!\n";

To print some more text, we can add another statement:

print "Hello, world!\n";
print "Goodbye, world!\n";

We can also group together a bunch of statements into a block—which is a bit like a paragraph—by surrounding them with curly braces{...}. We’ll see later how blocks are used to specify a set of statements that must happen at a given time, and also how they are used to limit the effects of a statement. Here’s an example of a block:

{
print "This is ";
print "a block ";
print "of statements.\n";
}

Notice how indentation is used to separate the block from its surroundings. This is because, unlike paragraphs, you can put blocks inside of blocks, which makes it easier to see on what level things are happening. This:

print "Top level\n";
{
print "2nd level\n";
{
print "3rd level\n";
}
print "Where are we?";
}

is easier to follow than this:

print "Top level\n";
{
print "2nd level\n";
{
print "3rd level\n";
}
print "Where are we?";
}

As well as curly braces to mark out the territory of a block of statements, you can use parentheses to mark out what you’re giving a function. The set of things given to a function are the arguments; and you pass the arguments to the function. For instance, you can pass a number of arguments to theprint()function by separating them with commas:

print "here ", "we ", "print ", "several ", "strings.\n";

The print()function happily takes as many arguments as it is given, and it produces the expected answer:

here we print several strings.

Surrounding the arguments with parentheses clears things up a bit:

print("here ", "we ", "print ", "several ", "strings.\n");

In the cases where parentheses are optional, the important thing to do is to use your judgment. Sometimes something will look perfectly understandable without the parentheses, but when you’ve got a complicated statement and you need to be sure of which arguments belong to which function, putting in the parentheses is useful. Always aim to help the readers of your code, and remember that these readers will more than likely include you.

Please check back for the conclusion to this article.